1. Field of the Invention
The present invention relates to optical products such as a camera lens and spectacle plastic lenses.
2. Description of Related Art
In plastic optical products, an optical multilayer film as an antireflection film is formed on the surface in order to reduce light reflection from the surface. Such an optical multilayer film is formed by alternately stacking several low refractive index and high refractive index layers, and an antireflection film having W-shaped spectral distribution of reflectance with a local maximum point at around 520 nm is commonly used in view of processing stability and appearance. Thus, upon incidence of light on the optical product having the optical multilayer film, a light green reflected image is seen when the optical product is viewed from the light incidence side (this phenomenon can also be seen in spectacle plastic lenses).
In order to make such a reflected image more faint and inconspicuous, the antireflection film needs to be designed to further reduce reflectance in a visible region in view of the cost. However, Japanese Patent Application Publication No. 2006-126233 (JP 2006-126233 A) shown below discloses design of an antireflection film having a seven-layer structure in which reflectance of light having an incident angle of 0 degrees is 1.0% or less in the wavelength range of 420 to 720 nm, although this design is produced in order to reduce reflections.
However, in the antireflection film of Japanese Patent Application Publication No. 2006-126233 (JP 2006-126233 A) as well, reflectance has a local maximum point of about 1% at around 580 nm (see reference number 21 in FIG. 2 of JP2006126233), and a light green reflected image is seen. Although the level of light transmittance and the degree to which reflection of outside light is reduced are relatively satisfactorily improved, the reflected color is still conspicuous.